As a method of forming silicon nanoparticles, such a physical manner has been known that silicon is heated and vaporized in an inert gas by excimer laser or the like, and also an in-gas vaporizing method is known (see Kanagawa-ken Sangyo Gijutu Sougou Kenkyusho Research Report No. 9/2003, pp 77-78). The latter method is configured to heat and vaporize the silicon by high-frequency induction heating or arc discharge instead of laser.
Such a CVD method is further known that a material gas is supplied into a CVD chamber, and silicon nanoparticles are formed on a heated substrate [see Japanese Laid-Open Patent Publication No. 2004-179658 (JP2004-179658A)].
In this method, nucleuses for growing silicon nanoparticles are formed on the substrate, and then the silicon nanoparticles are grown from the nucleuses.
However, the method of heating and vaporizing the silicon by laser irradiation cannot uniformly control an energy density for irradiating the silicon with the laser, and therefore it is difficult to uniformize the particle diameters and density distribution of silicon dots.
In the in-gas vaporizing method, the silicon is heated nonuniformly, and therefore the particle diameters and the density distribution of silicon dots cannot be uniformized without difficulty.
In the foregoing CVD method, the substrate must be heated to 550 deg. C. or higher for forming the nucleuses on the substrate, and the substrate of a low heat resistance cannot be employed, which narrows a selection range of the substrate material.
Accordingly, an object of the invention is to provide a method in which silicon dots having substantially uniform particle diameters and exhibiting a substantially uniform density distribution are formed directly on a silicon dot formation target substrate at a low temperature.
Also, it is an object of the invention to provide a silicon dot forming apparatus by which silicon dots having substantially uniform particle diameters and exhibiting a substantially uniform density distribution can be formed directly on a silicon dot formation target substrate at a low temperature.